Battery chargers are used in portable electronic systems to charge and sometimes condition secondary batteries. Recently, emphasis on design for chargers of such systems has been on reducing their size and cost and increasing their portability. Consumer cellular telephones, notably those manufactured by Motorola, Inc., have undergone a quantum leap in recent years in their reduction in size and weight. Consumers now expect a commensurate increase in the portability of their associated charging systems. Unfortunately, no charging system for use in an automobile has proven completely satisfactory in terms of portability and convenience to the user. Therefore, there exists a need for an improved battery charger for use in an automobile.